There are many types of data processing devices including computer terminals, wireless personal digital assistants (“PDAs”) and network servers. Data objects such as calendar entries, e-mail messages and data objects are frequently shared between two or more data processing devices. When a copy of a particular data object is stored on both a computer terminal and a server that serves the computer terminal, for example, the stored data object can be independently modified (i.e. edited, added, deleted, moved, . . . etc) on both the computer terminal and the server. Commonly, after the data object is modified on the computer terminal, the data object is then transmitted back to the server to be stored in place of the original data object, so that the copy of the data object remains up-to-date on both the computer terminal and the server.
One technique for ensuring that the data object on the server is synchronized with the data object on the computer terminal is for the server to assign a unique data object ID to each original data object when the server initially stores the data object. Subsequently, when the computer terminal retrieves the data object, the retrieved data object includes the unique data object ID. If the data object is modified at the computer terminal and transmitted back to the server, as described above, the data object is identified by the server with the same unique data object ID.
Another data sharing technique reduces network data traffic by sending only the actual edits (i.e., the difference between the original data object and the edited data object) rather than the complete, edited data object between the computer terminal and the server. For example, the computer terminal retrieves and edits a data object from the server which is identified with a particular data object ID. The data object is then edited at the computer terminal (e.g., by deleting the third line and changing the third word in the second line from “less” to “more”). The actual edits (i.e. delete the third line and replace the third word in the second line from “less” to “more”) and the data object ID of the document data object are then sent to the server. The server then executes the modifications to the data object with the same data object ID stored on the server.
The actual network bandwidth of the computer network is often limited to the lowest bandwidth of the any one portion of the network connecting the computer terminal and the server. For example, if the server is linked to the computer terminal via a 14.4 kbps wireless connection, then the maximum through put to the computer terminal is 14.4 kbps even though some portions of the network may have a wider bandwidth (e.g., a 1.4 Mbit T1 line, 10 Mbit Ethernet, . . . etc).
In addition, certain wireless networks suffer frequent interruptions due to radio frequency interference and lack of network coverage. A wireless network connection may be interrupted, for example, if the wireless data processing device passes through a tunnel or some other obstruction or into an area without wireless network coverage. Because the wireless network may be interrupted and may often have a relatively low bandwidth, it is important to minimize the data traffic across the wireless network.
FIG. 1 shows a prior art process where a data object is added to a computer terminal such as a wireless user terminal in block 105. A copy of the data object is sent to the server in block 110. The server then assigns an ID to the data object in block 115. The server sends the data object ID back to the user terminal so that the user terminal can identify that data object. As discussed above, the data object ID code allows the user terminal and the server to refer to the correct data object by the assigned ID.
In a block 125, the data object is edited in the user terminal. In block 130, a copy of the edits are sent to the server along with the data object ID. The server uses the ID to properly identify and edit the data object and then updates the correct data object according to the edits, in block 140.